Renaming a namespace's prefix

Question

I have a TTL file like so:

@prefix owl: <http://www.w3.org/2002/07/owl#> .
@prefix : <http://example.com#> .

:Custom_Object a owl:Class .

Ideally using rdflib or similar, I would like to load this file and change the prefix for http://example.com namespace to something else. After re-serializing the graph, it should look something like:

@prefix owl: <http://www.w3.org/2002/07/owl#> .
@prefix example: <http://example.com#> .

example:Custom_Object a owl:Class .

I have tried using rdflib's Graph.bind() but it seems to only work the other way (changing the namespace but NOT the prefix).